The present invention relates to a magnetic head and a recording/reproducing apparatus that uses the same, more particularly to a magnetic head including a magnetoresistive sensor and a magnetic recording/reproducing apparatus that uses the same.
The high recording density magnetic recording technique that mainly handles hard disk drives uses such a magnetoresistive head as a read sensor. The read sensor depends significantly on the performance of the magnetic recording technique. While the recording density of magnetic recording/reproducing apparatuses has been improved rapidly, none of the prior techniques has realized a magnetoresistive head having both sensitivity and output with good symmetric performance for external magnetic field to meet the requirements of very high recording density magnetic recording/reproducing apparatuses, particularly their reproducing parts. It has thus been difficult for the prior techniques to realize the functions required for the apparatuses to be employed as storage devices.
In recent years, it has been well known that a large magnetoresistance, that is, a so-called giant magnetoresistance, is recognized in a multilayer consisting of ferromagnetic metallic layers separated by a non-magnetic metallic layer from each other. The giant magnetoresistance is a phenomenon that the electrical resistance changes according to an angle of the magnetizations between two ferromagnetic layers separated by a non-magnetic intermediate layer. If this giant magnetoresistance is applied to a magnetoresistive sensor, a structure referred to as a spin-valve should also be employed for the structure. In other words, the spin-valve is structured to include an antiferromagnetic film, a ferromagnetic layer, a non-magnetic intermediate layer, and a soft magnetic free layer that are laminated in order. The spin-valve functions to pin the magnetization of a ferromagnetic layer stuck fast to an antiferromagnetic film due to an exchange coupling field generated in an antiferromagnetic film/ferromagnetic layer interface substantially so that the other soft magnetic free layer is magnetized and its magnetizing direction is rotated by an external magnetic field, thereby obtaining an output. Hereinafter, the above pinning effect will be referred to as pinning bias and an antiferromagnetic film that generates such an effect will be referred to as a pinning bias layer. A ferromagnetic layer having a magnetizing direction pinned substantially will be referred to as a pinned layer or ferromagnetic pinned layer. Similarly, a soft magnetic layer that is magnetized with its magnetizing direction rotated by an external magnetic field will be referred to as a free layer or soft magnetic free layer.
A pinned layer has a magnetizing direction pinned substantially with respect to a magnetic field to be perceived. Its antimagnetic film may be replaced with a hard magnetic film, that is, a material having a magnetizing direction that is to be changed only by application of a comparatively large magnetic field respectively. As is well known, anti-parallel coupled high coercivity film, that is, a so-called self-pin, is used as a hard magnetic film. In recent years, it is also proposed to use a multilayer consisting of ferromagnetic pinned layers having a specular effect and/or synthetic ferrimagnet. However, they are all the same in that the magnetizing direction of a ferromagnetic layer at interface contact with a non-magnetic intermediate layer directly is substantially pinned. The tunneling magnetoresistance, that is, a current-perpendicular-to-the-plane type magnetoresistive sensor referred to as a so-called TMR is also the same as that in the basic structure.
The magnetoresistive head has a domain control structure for stabilizing the domain of a soft magnetic free layer. This domain control structure enables a soft magnetic free layer to stabilize its single domain structure to provide a no hysteresis output with a magnetic field to be perceived. The hard bias, which has a typical domain control structure, is configured as shown below. A hard magnetic film is provided at both ends of a magnetoresistive film formed in the track width at a predetermined thickness. The hard magnetic film is magnetized so as to have some residual magnetization in the track width direction in a magnetizing process and that residual magnetization enables canceling of both of the magnetic charge generated at the track width end portion and the magnetic charge generated at the end portion of the soft magnetic free layer mutually to lower the static magnetic energy and perform single domain-stabilization of the soft magnetic free layer.
There is also proposed an in-stack type domain control structure as a domain control structure corresponding to higher recording density. In this structure, domain control layers are laminated on a magnetoresistive film. All the domain control layers are formed almost in the track width so that they are self-aligned at their ends for enabling domain control. The following discussion will refer to these references:    Patent document 1: U.S. Pat. No. 5,408,377;    Patent document 2: Official gazette of JP-A No. 259824/1999;    Patent document 3: U.S. Pat. No. 6,023,395;    Patent document 4: Official gazette of JP-A No. 025013/2002;    Patent document 5: U.S. Pat. No. 6,473,279;    Patent document 6: Official gazette of JP-A No. 367124/2002; and    Non-patent document 1: JOURNAL OF APPLIED PHYSICS VOLUME 92, 2646-2650 (2002), H. Yuasa, M. Yoshikawa, Y. Kamiguchi, K. Koi, H. Iwasaki, M. Takagishi, and M. Sahashi, “Output enhancement of spin-valve giant magnetoresistance in current-perpendicular-to-plane geometry.”